A variety of fluid analysis cell assemblies have been designed and implemented for use in analyzing fluid samples, particularly in analytical chemistry applications. Such fluid cell assemblies may be constructed to statically hold a pre-designated volume of fluid to be analyzed, or may instead be configured as a flow cell, which are typically used to transport fluid samples through an analysis chamber.
In flow cell arrangements, fluid samples are typically transported through a chamber disposed between a radiant energy source and a radiant energy detector, which detector measures the relevant radiant energy wavelength absorption or transmission through the fluid sample. An example of such a detector is a spectrophotometer. Various analytical instruments then utilize the absorbed versus transmitted radiant energy to determine the composition of the associated fluid sample.
To efficiently pass the radiant energy through the fluid sample in the analysis chamber, however, the wall defining the fluid-containing chamber is preferably a material having an index of refraction that is less than that of the fluid sample. Such an index of refraction relationship between the fluid sample and the analysis chamber wall assists in internally reflecting, and thereby propagating the radiant energy waves through the fluid sample analysis chamber. Description of this phenomenon is found in U.S. Pat. Nos. 6,678,051 and 6,734,961, which are assigned to the same assignee in the present application, and which are herein incorporated by reference.
In order to best utilize aqueous fluid samples, therefore, a material having an index of refraction less than that of water is needed to at least form a liner of the fluid analysis chamber wall. One such material is a fluorinated polymer product sold by E.I. du Pont de Nemours and Company of Wilmington, Delaware under the trade name Teflon AF®. It is therefore a desired aspect of the fluid analysis cells of the present invention to incorporate a layer of Teflon AF® or other low index of refraction material therewithin to allow efficient radiant energy propagation in spectrophotometry applications.
While various such fluid sample analysis cells and assemblies are currently utilized in the field, certain operational and implementational deficiencies exist. For example, multi-unit flow cell assemblies have found difficulty in being hydraulically sealed to one another when relatively rigid materials such as stainless steel are desired in the fabrication of the bulk cell body parts. In addition, methods for installing radiant energy guiding elements into such flow cells, and particularly those manufactured from stainless steel, have been met with limited success, or are relatively inefficient and expensive to implement.
It is therefore a principal object of the present invention to provide an improved fluid sample analysis apparatus having design features enabling the use of a plurality of distinct metallic cell bodies in fluid connection and hydraulically sealed with one another.
It is another object of the present invention to provide an assembly methodology for installing a radiant energy guiding member into a fluid analysis cell body.
It is a further object of the present invention to provide an outer housing for frictionally securing a multi-unit flow cell assembly in axial alignment therewithin.